1. Field of the Invention
The present invention relates to a method for fabricating a liquid crystal display (LCD) device, and more particularly, to a method for fabricating a color filter substrate.
2. Discussion of the Related Art
With the recent development in display devices of advanced technology and skills such as high definition televisions, various flat display devices have been actively researched, for example, liquid crystal displays (LCD), electroluminescence displays (ELD), vacuum fluorescent displays (VFD), and plasma display panels (PDP), which can substitute for cathode ray tubes (CRT).
Among the various flat display devices, the LCD device has been most widely used due to the advantageous characteristics of thin profile, lightness in weight, and low power consumption. Accordingly, the LCD devices are used for a mobile-mounting type monitor and a monitor of a color television as well as a laptop computer and a pocket computer.
The LCD device having the aforementioned characteristics includes an upper substrate of a color filter array substrate, a lower substrate of a thin film transistor TFT array substrate, and a liquid crystal layer. At this time, the liquid crystal layer is formed between the lower and upper substrates, wherein the liquid crystal layer has the dielectric anisotropy.
In more detail, the color filter substrate is comprised of a color filter layer having red R, green G and blue B color filter patterns, a black matrix layer, and a common electrode. At this time, the color filter layer has the R, G and B patterns arranged in order, to represent various colors. Then, the black matrix layer divides R, G and B cells, and prevents light from being incident on predetermined portions of the color filter substrate. Also, the common electrode provides a voltage to a liquid crystal cell. As the R, G and B patterns of the color filter layer are driven separately, the color of one pixel is represented by combination of the three R, G and B patterns.
Hereinafter, a method for fabricating a color filter substrate according to the related art will be described with reference to the accompanying drawings.
FIG. 1A to FIG. 1G are cross sectional views of the process for fabricating a color filter substrate according to the related art.
First, after cleaning a glass substrate 11, as shown in FIG. 1A, a metal thin layer of chrome Cr, having an optical density OD of 3.5 or more, or an organic layer of carbon type is deposited on the glass substrate, and patterned by photolithography, thereby forming a black matrix 13.
The black matrix 13 is formed in correspondence with an edge of a unit pixel region, and an area for forming a thin film transistor TFT, thereby preventing light from leaking through the edge of the unit pixel region and the area for forming the thin film transistor TFT, which have a relatively unstable electric field.
After forming the black matrix 13, a color resist is coated on an entire surface of the glass substrate 11 including the black matrix 13, to represent various colors. That is, a first color resist 14a of a red color is coated to completely cover the entire surface of the black matrix 13.
Subsequently, as shown in FIG. 1B, after masking predetermined portions of the first color resist 14a with light-shielding parts of a mask 17, ultraviolet rays are irradiated thereon, thereby partially exposing the first color resist 14a. 
Next, as shown in FIG. 1C, the first color resist 14a, having a changed photochemical structure by exposure, is cured at a high temperature of about 230° C., and then is dipped into a developing solution, thereby forming a first color pattern 15a of red color. At this time, the developing process may be performed in any one of dipping, puddle and shower spraying.
As shown in FIG. 1D, a second color resist 14b of a green color is coated on the entire surface of the glass substrate having the first color pattern 15a of red color. Then, after masking predetermined portions of the second color resist 14b with the light-shielding parts of the mask 17, ultraviolet rays are irradiated thereon, thereby partially exposing the second color resist 14b. At this time, the mask 17 is the same one used when exposing the first color resist 14a. That is, after exposing the first color resist 14a, the mask 17 is shifted to expose the second color resist 14b. 
The second color resist 14b, having a changed photochemical structure by exposure, is developed, as shown in FIG. 1E, thereby forming a second color pattern 15b of green color.
The second color pattern 15b is formed in one pixel region adjacent to another pixel region having the first color pattern 15a, wherein the black matrix 13 is formed between the two pixel regions of the first color pattern 15a and the second color pattern 15b. 
Subsequently, a third color resist 14c of a blue color is coated on the entire surface of the glass substrate including the second color pattern 15b. Then, after masking predetermined portions of the third color resist 14c with the light-shielding parts of the mask 17, ultraviolet rays are irradiated thereon, thereby partially exposing the third color resist 14c. At this time, the mask 17 is the same one used when exposing the first and second color resists 14a and 14b. That is, after exposing the first and second color resists 14a and 14b, the mask 17 is shifted to expose the third color resist 14c. 
The third color resist 14c, having a changed photochemical structure by exposure, is developed, as shown in FIG. 1F, thereby forming a third color pattern 15c of blue color.
The third color pattern 15c is formed in one pixel region adjacent to another pixel region having the second color pattern 15b, wherein the black matrix 13 is formed between the two pixel regions of the second color pattern 15b and the third color pattern 15c, thereby completing a color filter layer 15 of R, G and B patterns.
Generally, the color filter layer 115 is formed in order of R, G and B patterns.
After that, as shown in FIG. 1G, a planarization layer is coated on the entire surface of the glass substrate including the color filter layer 15, to protect the color filter layer 15 and to planarize the entire surface of the color filter layer 15, thereby forming an overcoat layer 16. At this time, the planarization layer is formed in a method of coating acrylic resin or polyimide-type resin by spin coating.
Then, a transparent electrode material such as ITO (Indium-Tin-Oxide), having great transmittance, high conductivity and stable chemical and thermal characteristics, is deposited on the overcoat layer 16 by sputtering, thereby forming a common electrode 18. When forming the common electrode 18, it is unnecessary to perform an additional patterning process. The common electrode 18 drives a liquid crystal cell with a pixel electrode formed on a TFT array substrate.
Accordingly, it is possible to complete a color filter substrate having the black matrix 13, the color filter layer 15, the overcoat layer 16 and the common electrode 18.
For reference, in case of an In-Plane Switching (IPS) mode LCD device, a common electrode is formed on a TFT array substrate, and a black matrix, a color filter layer and an overcoat layer are formed on a color filter substrate.
However, the method for fabricating the color filter substrate according to the related art has the following disadvantages.
In case of the method for fabricating the color filter substrate according to the related art, it is necessary to change the color resist by R, G and B, in order to change the chromatic coordinates of the color filter layer. That is, the patterning process for forming the R, G and B patterns is performed several times. In addition, the overcoat layer is additionally formed to planarize the irregular color filter layer. Accordingly, the fabrication process is complicated, and the fabrication time increases.